When operating fuel injectors having a magnetic coil drive, different chronological opening behaviors of the individual injectors and therefore variations in the respective injection quantity occur because of electrical tolerances.
The relative injection quantity differences from injector to injector and from injection to injection increase as injection times and/or electrical/hydraulic separation times become shorter. These relative quantity differences have heretofore been small and without practical significance. The development in the direction of smaller and more injection quantities and injection times per injection cycle (multiple injections) has had the result that the influence of the relative quantity differences can no longer be left out of consideration. In particular in the case of injections in short succession, a residual magnetization present in the magnetic coil drive can be present from the preceding injection, which can influence the following injection.
In some examples, the injector voltage of the last injection procedure is ascertained before a next injection to conclude a pre-magnetization state of the injector and react in a suitable manner. Furthermore, this alternatively may be carried out by a defined supply voltage and the flowing current linked thereto be obtained as a measure of a residual magnetization.